System for mobile radio communication and a method relating to service provision in mobile radio communication networks

ABSTRACT

The present invention relates generally to a method and apparatus for selecting a visited mobile radio network upon international roaming. More particularly, the invention relates to selecting a mobile radio network with regard to the support given by the mobile radio network in respect of a network feature. An international roaming indication is provided to the home mobile radio network of a mobile station, indicating that the mobile station is roaming, or is intending to roam, internationally. Such international roaming indication comprises information about geographic region(s) in which it is likely that the mobile station will communicate. The home mobile radio network then selects at least one mobile radio network, operated in the geographic region(s) and supporting the network feature needs of the mobile station, and sends information to the mobile station regarding the selected mobile radio network(s).

FIELD OF THE INVENTION

[0001] The present invention relates generally to the field of mobileradio communications, and more particularly to a method and apparatusfor selecting a visited mobile radio network upon international roaming.

BACKGROUND

[0002] A subscriber to services in a mobile radio network can benefitfrom a large number of different services provided by the mobile radionetwork. Besides basic bearer services such as speech and data calls,most mobile radio networks also provide supplementary services such ascall forwarding, virtual private networks, pre-paid etc. In moststandards for mobile radio communication, some of these supplementaryservices are standardised and hence provided by all mobile radionetworks based on the same standard. However, many supplementaryservices are also specific to a certain mobile radio network, and do notexist in other mobile radio networks based on the same standard. If nospecial action is taken, a subscriber to such a network-specificsupplementary service will therefore not be able to use the service whenhe leaves his home mobile radio network.

[0003] In the standards of Global System for Mobile communications (GSM)and Universal Mobile Telephony System (UMTS) a network feature has beenimplemented to address this problem. This network feature is referred toas Customized Application for Mobile network Enhanced Logic (CAMEL), andintroduces a possibility for the mobile radio networks involved in acall to/from a roaming subscriber to exchange information about theservices to which the roaming subscriber subscribes. CAMEL is describedin the GSM Technical Specifications 02.78, 03.78, 09.02, and 09.78 aswell as in the 3rd Generation Partnership Project TechnicalSpecifications 22.078, 23.078, 29.002 and 29.078.

[0004] An apparatus comprising a database, a generator and a dataproviding device wherein the generator generates a list of preferredwireless carrier identities based upon a selected class of service,predetermined national accounts and predetermined home market areas isdisclosed in U.S. Pat. No. 6,148,197.

SUMMARY

[0005] A problem to which an aspect of the present invention relates ishow to enable improved service for a subscriber to services in a mobileradio network when the subscriber performs international roaming.

[0006] This problem is addressed by a method for selecting a visitedmobile radio network for a mobile station performing internationalroaming, the mobile station being associated with a subscription toservices in a home mobile radio network. The method is characterised inthat the need of a network feature of the subscription is considered inselecting the visited mobile radio network.

[0007] The problem is further addressed by a system for mobile radiocommunication comprising mobile radio networks, each mobile radionetwork enabling mobile radio communication for mobile stationsregistered with the mobile radio network. The system is characterised bymeans for taking into account the needs of a network feature of a mobilestation when selecting a visited mobile radio network for said mobilestation.

[0008] By the inventive method and system is achieved that a user of amobile station will experience improved support for network features, towhich the user subscribes, when performing international roaming.

[0009] In one embodiment of the inventive method, a list of preferrednetworks, comprising the identity of at least one network which supportssaid need of a network feature of the subscription, is compiled. Thelist of preferred networks is then sent to and stored at the mobilestation. In the inventive system, the means for taking into accountcould further comprise means for compiling a list of preferred mobileradio networks, containing identities of mobile radio networks whichgives support for the network feature needs of said mobile station, andsending means for sending the list of preferred mobile radio networks tothe mobile station.

[0010] Hereby is achieved that the list of preferred networks stored inthe mobile station comprises identities of mobile radio networks whichsupport the network feature needs of the mobile station. Upon failure toregister with the home mobile radio network, the mobile station canselect a mobile radio network from said list of preferred mobile radionetworks as the visited mobile radio network with which the mobilestation should try to register. In this embodiment, the identities ofthe preferred mobile radio networks can be placed in order of preferenceaccording to a predefined criterion.

[0011] In one embodiment of the invention, the inventive methodcomprises the step of receiving, in the home mobile radio network, aninternational roaming indication associated with the subscription. Theinternational roaming indication comprises information on geographicalregion(s). The geographical region(s) are then considered, together withthe network feature needs of the mobile station, in selecting thevisited mobile radio network. In the inventive system, the means fortaking into account could further comprise receiving means for receivingan international roaming indication associated with said mobile station,said international roaming indication comprising information ongeographical region(s).

[0012] Hereby is achieved that the mobile radio network selected as thevisited mobile radio network is operated in the area where the mobilestation is located. In one aspect of this embodiment, the internationalroaming indication is a location update request comprising an identityof the mobile station, the identity of the mobile radio network to whichthe mobile station is trying to register and a not preferred indicator.The information on geographic region(s) consists of the identity of themobile radio network to which the mobile station is trying to register.In this aspect, the receiving means could comprise means for receiving alocation update request containing a not preferred indicator. Hereby isachieved that the sending of the international roaming indication isautomatic. In this aspect, the identity of a selected visited mobileradio network can be included in a location update result message, sentto the mobile station in response to receiving said location updaterequest.

[0013] In one embodiment of the inventive method, a set of mobile radionetworks, out of which the visited mobile radio network can be selected,is arranged in an array. Each array entry represents a geographic areaand each mobile radio network in the set is associated with at least onearray entry representing a geographic area in which the mobile radionetwork is operated. Each mobile radio network in the set is furtherassociated with information on the network feature support provided bythe mobile radio network. In the inventive system, the means for takinginto account could further comprise a first storage for storinginformation on which (if any) level(s) of capability of said networkfeature that each of the mobile radio networks in a set of mobile radionetworks supports and a second storage for storing information onlevel-of-capability needs of a subscription, associated with said mobilestation, with regard to said network feature.

[0014] Hereby is achieved that the finding of a visited network, whichsupports the network feature needs of the mobile station and is operatedin the geographic area where the mobile station is located, isfacilitated. In one aspect of this embodiment, the geographic arearepresented by an array entry corresponds to the coverage area of amobile radio network, which is not necessarily included in the set ofmobile radio networks. The coverage area of each of the mobile radionetworks in the set should preferably be represented by an entry in thearray in this aspect of the embodiment. In another aspect of thisembodiment, the mobile radio networks in the array are placed in orderof preference according to a predefined criteria. In a third aspect ofthis embodiment, there is associated an indicator to each mobile radionetwork in the set, indicating whether the mobile radio network is afavourable mobile radio network. The value of this indicator is thentaken into account in selecting a visited mobile radio network. Herebyis achieved that e.g. the operator of the home mobile radio network canpoint out the mobile radio networks which the operator for some reasonsfinds more suitable for subscribers in the home mobile radio network.

[0015] The problem addressed by this invention is further met by amobile station for communicating in a mobile radio system. The mobilestation is associated with a subscription to services in a home mobileradio network and comprises a storage for storing a list of preferredmobile radio networks. The mobile station is capable of sending alocation update request comprising a not preferred indicator to the homemobile radio network when trying to register with a mobile radio networkother than the home mobile radio network or the mobile radio networkslisted in the list of preferred mobile radio networks.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will now be discussed in more detail withreference to preferred embodiments of the present invention, given onlyby way of example, and illustrated in the accompanying drawings, inwhich:

[0017]FIG. 1 schematically illustrates a mobile station communicating inits home mobile radio network, the network being operated in a homenetwork area. Also shown is a geographic area not covered by the homemobile radio network, in which three different mobile radio networks areoperated.

[0018]FIG. 2 is an example of a country array which could be used whencompiling a preferred networks list.

[0019]FIG. 3 schematically illustrates a flowchart describing oneembodiment of the inventive method.

[0020]FIG. 4 is an example of a region array which could be used whencompiling a preferred networks list.

[0021]FIG. 5 is an example of a country array in which each array entryis represented by the coverage area of a mobile radio network.

[0022]FIG. 6 is a schematic flowchart describing an embodiment of theinventive method in which the international roaming indication isincluded in a location update request message.

[0023]FIG. 7 is an exemplary signalling diagram describing the flow ofmessages when the international roaming indication is included in thelocation update request.

DETAILED DESCRIPTION

[0024] An exemplary mobile radio network 100, or simply network 100, isschematically illustrated in FIG. 1. Network 100 comprises at least oneradio base station 105 and provides mobile radio communication to usersof Mobile Stations (MSs) within a limited geographic area, often boundedby international borders. An exemplary MS 110, associated with asubscription to services provided by network 100, is shown communicatingvia signalling link 115 in FIG. 1. The term mobile station includes anyterminal or network offering packet- or circuit-related connectivity innetwork 100. The exemplary network 100 in FIG. 1 is shown to be a GSMnetwork, but the present invention could be applied to networks 100 ofany standard.

[0025] Network 100 is the home mobile radio network of MS 110, andnetwork 100 will hereinafter be referred to as home network 100. Thegeographic area to which home network 100 is limited will be referred toas the home network area 120. As long as MS 110 stays within the homenetwork area 120, home network 100 will provide MS 110 with the servicesto which the user of MS 110 is subscribing. These services could e.g. bebearer services such as speech or data, as well as supplementaryservices such as pre-paid or call forwarding.

[0026] Home network 100 further comprises a Home Location Register (HLR)125, in which information on all subscribers to services in home network100 are stored. Such subscriber information could e.g. be identity (suchas phone-number) and subscribed services.

[0027] When MS 110 leaves home network area 120 to enter anothergeographic area, MS 110 performs what will hereinafter be referred to asinternational roaming. MS 110 can then no longer benefit from the bearerservices provided by home network 100. However, outside of home networkarea 120, there are several other mobile radio networks, hereinafterreferred to as networks 130, providing services to MSs. In FIG. 1, ageographic area 135 is shown, in which three networks 130A, 130B and130C are operated, each represented by a radio base station 105A, 105Band 105C, respectively. MS 110 could therefore, by registering with oneof networks 130A, 130B or 130C, still use mobile services in geographicarea 135. A network 130 with which MS 110 registers when entering ageographic area not covered by the home network 100 will in thefollowing be referred to as a visited network.

[0028] A list is stored in MS 110, listing some networks 130 in whichsubscribers in home network 100 are allowed to communicate according toroaming agreements between home network 100 and the networks 130 in thelist. This list will in the following be referred to as the preferrednetworks list. Since the number of networks 130, with which home network100 has roaming agreements, is typically large compared to the number ofentries reserved for networks 130 in the preferred networks list, theremost likely exist other networks 130, not listed in the preferrednetworks list, in which subscribers in home network 100 are also allowedto communicate.

[0029] In following the existing procedure for selecting a visitednetwork when entering a geographic area 135, MS 110 selects the firstnetwork 130 in the preferred networks list and tries to register withthis selected network. If the selected network is any of networks 130A,130B or 130C, this registration trial will probably be successful,depending e.g. on present load in the selected network. However, if theselected network is not any of networks 130A, 130B or 130C, then theregistration trial will fail. MS 110 will then try to register with thenext network 130 in the preferred networks list. If MS 110 is notsuccessful in registering with any of the networks 130 in the preferrednetworks list, then MS 110 will check the signal strengths perceivedfrom the surrounding networks 130. In a mobile radio system operatingaccording to the GSM standard, the MS 110 will build a list of thenetworks 130 from which it can perceive a signal strength >85 dB, andtry to register with the networks 130 in this list. If MS 110 is notsuccessful in registering with any of the networks 130 in the list, e.g.because home network 100 does not have roaming agreements with thenetworks 130 in the list, then MS 110 builds another list of networks130 from which it can perceive a signal strength <85 dB. MS 110 willthen try to register with the networks in this other list. The existingprocedure for selecting a network 130 to which MS 110 should try toregister according to other standards of mobile telephony, such as e.g.the UMTS standard, are also based on measurements of the signal strengthof surrounding networks 130.

[0030] Had all the networks 130 present in a geographic area 135 beenidentical apart from the signal strengths provided in different parts ofgeographic area 135, then the above described existing procedure forselecting a visited network would always have resulted in the bestservice available for MS 110. However, in some respects, networks 130present in the same geographic area 135 are most likely to differ. Onesuch respect is the version of CAMEL that has been implemented in thenetworks 130.

[0031] If both the visited network and the home network 100 haveimplemented CAMEL, a MS 110 to which a CAMEL subscription is associatedwill be able to benefit from services specific to home network 100. Whena service specific to home network 100 is invoked, the call is switchedin the visited network under the control of the home network 100, andthe service specific to the home network 100 is executed in the homenetwork 100, despite that the MS 110 is roaming elsewhere.

[0032] However, not all GSM or UMTS mobile radio networks haveimplemented the CAMEL feature. If a MS 110, associated with asubscription to network-specific supplementary services, performsinternational roaming and registers in a network 130 which does notsupport CAMEL, the network-specific supplementary services will not workat all. This can be a very severe problem to the user of MS 110. If,e.g., the subscription is part of a Virtual Private Network (VPN) withcalls outside the VPN barred, and the VPN has been implemented as anetwork-specific supplementary service which relies on CAMEL, the userof MS 110 will not be able to use the MS 110 for any calls but emergencycalls in a network 130 that does not support CAMEL.

[0033] Although many networks 130 have implemented CAMEL, the CAMELfeature is evolving and different phases of the feature have beenreleased by the standardisation fora. Hence, different phases of thefeature have been implemented in different networks 130. Each phase ofCAMEL has different capabilities and possibilities to supportnetwork-specific supplementary services. Thus, when a MS 110 roams in anetwork 130 which has implemented a less elaborated phase of CAMEL thanthe home network 100, it is likely that the network-specificsupplementary services to which the user of MS 110 subscribes will notfunction the way the user expects them to.

[0034] Since no selectivity with regard to CAMEL capabilities, or anyother network features, is introduced in the above described existingprocedure for selecting a visited network, MS 110 may end up registeringwith a visited network which does not at all support the needs of thenetwork feature that the MS 110 has, even in situations when there existnetwork(s) in the geographic area 135, in which MS 110 is roaming, thatdoes support the needs of MS 110 and in which subscribers in homenetwork 100 by a roaming agreement are allowed to communicate.

[0035] In the inventive method for selecting a visited network for a MS110, an international roaming indication is provided to the home network100, indicating that MS 110 is roaming, or is intending to roam,internationally. Such international roaming indication comprisesinformation about geographic region in which it is likely that MS 110will communicate. The international roaming indication could then beprocessed by the home network 100, and a new preferred networks listcould be compiled and downloaded to MS 110, the new preferred networkslist comprising networks 130 providing services in the geographic regionindicated in the international roaming indication. If MS 110 is thenunsuccessful in registering with home network 100, MS 110 tries toregister with the first network 130 in the new preferred networks list.If this registration trial is not successful, MS 110 tries to registerwith the next network 130 in the new preferred networks list. If MS 110is not successful in registering with any of the networks 130 listed inthe new preferred networks list, then MS 110 tries to register with oneof the networks 130 from which MS 110 can perceive a radio signal.

[0036] The new preferred networks list could be tailor-made to suit theneeds of MS 110 as well as the objectives of the operator of homenetwork 100. When compiling the new preferred networks list, the homenetwork 100 could e.g. choose to put networks 130 at the top of the listwhich home network 100 has an owner's interest in, or with which homenetwork 100 has favourable agreements.

[0037] The international roaming indication could be provided to thehome network 100 e.g. by the user of MS 110 giving a phone-call to acustomer care operator, or sending information via a network servicesuch as e.g. the Wireless Application Protocol (WAP), the World Wide Web(WWW), the Short Message Service (SMS) or an Intelligent Network (IN)service. In case of the international roaming indication being sent tothe home network 100 via a network service, the international roamingindication could preferably comprise entries, each entry representing ageographic region.

[0038] The international roaming indication could alternatively beincluded in the location update request sent from the MS 110. Thesending of the international roaming indication would then be automatic.The MS 110 could e.g. include a parameter in the location updaterequest, indicating that the network 130, with which the MS 110 ispresently trying to register, is not one of the networks 130 included inthe preferred networks list, stored in the MS 110. Such parameter willin the following be referred to as the not preferred indicator. Since alocation update request includes the identity of the mobile radionetwork 130 with which the MS is trying to register, the identity of themobile radio network 130 could be used to identify the geographic areain which the MS 110 is presently active. A location update request alsoincludes more detailed information on the location of the MS 110, whichcould be used to identify adjacent geographic areas which could possiblybe of interest to MS 110. For details on location updating, see e.g. GSMTechnical Specification 09.02.

[0039] The international roaming indication could be processed by theHLR 125, or by any other node(s) connected to home network 100.Alternatively, parts or all of the processing of the internationalroaming indication could be performed by a human being. The preferrednetworks list could be sent to MS 110 by use of SMS, or any othernetwork service which allows the home network 100 to downloadinformation to MS 110. In case of the international roaming indicationbeing included in location update request, a preferred networks listcould be included in the location update result message sent from thenetwork to the MS 110. The preferred networks list could then be storedin MS 110. In GSM, the preferred networks list could e.g. be stored inthe MS 110 by use of an existing toolkit referred to as the SIM(Subscriber Identity Module) application toolkit.

[0040] In order to facilitate for the selection of networks 130 to beentered in the preferred networks list, an array could be kept at a nodein the home network 100, such as e.g. the HLR 125, or at any other nodeconnected to the home network 100. The array could comprise networks 130with which home network 100 has a roaming agreement, the networks 130 inthe array being arranged e.g. according to in which geographic area(s)networks 130 are operated. An example of such an array of geographicareas is shown in FIG. 2, in which the geographic areas are referred toas countries. It should be understood that the term “country” does nothere necessarily mean “country” in the political sense, but could e.g.refer to a geographic region in which the available radio frequenciesare administered by the same authority. Shown in FIG. 2 is country array200, into which three country entries 205, each representing a country,have been entered. To each country entry 205 is linked a networks list210, listing identities of the networks 130 present in the countryassociated with country entry 205 and with which home network 100 has aroaming agreement. To each entry in the networks list 210 is linked acapabilities list 215, listing the phases, or levels of capabilities, ofa network feature supported by the network 130 associated with thatentry. The entries in each network list 210 could be arranged so thatthe identity of the network 130, which the home network 100 according tosome criterion (or criteria) finds to be the preferred network 130, isat the top of the network list 210, the identity of the second bestnetwork 130 at the second position in the network list 210 etc. Thecriterion could e.g. be the level of radio coverage of the networks 130,ownership of the networks 130, or any other criterion.

[0041] In FIG. 3, a flowchart describing an example of the method of theinvention is presented.

[0042] The example of FIG. 3 is, for the purpose of illustration,presented in relation to the network feature known as CAMEL. Theinventive method could, however, be applied in relation to any networkfeature, such as e.g. the General Packet Radio Service (GPRS). In step300, an international roaming indication is received by the home network100 from the user of MS 110, or from MS 110. The international roamingindication comprises entri(es), each entry corresponding to a country.The international roaming indication could be transferred to homenetwork 100 by the user of MS 110 giving a phone-call to a customer careoperator, or sending information via a network service such as e.g. theWireless Application Protocol (WAP), the World Wide Web (WWW), the ShortMessage Service (SMS) or an Intelligent Network (IN) service.Alternatively, the international roaming indication could be included ina location update request.

[0043] The international roaming indication is then processed by homenetwork 100, e.g. in HLR 125. In step 305, the specific CAMEL needs ofMS 110 stored in the HLR 125 are checked, and the maximum (mostelaborated) and minimum (least elaborated) levels of capability of CAMELthat would satisfy the network feature capabilities needs of MS 110 areselected. Step 310 is then entered, in which the first country in theinternational roaming indication is selected. In step 315 it is checkedwhether the country selection in step 310 was successful. If not, thenstep 370 is entered where it is checked whether a preferred networkslist has been compiled. Since no preferred networks list has beencompiled in the case where no country at all was found in theinternational roaming indication, step 380 is entered where theprocedure is exited. However, if the outcome of the check in step 315 isthat a country was successfully selected in step 310, then step 320 isentered. In step 320, the country array 200 is scanned in order to lookfor a country entry 205, matching the country selected in step 310, toselect. In step 325, it is checked whether a country entry 205 has beenselected in step 320. If not, then step 310 is re-entered where the nextcountry in the international roaming indication is selected. However, ifa matching country entry 205 was successfully selected, then step 330 isentered. In step 330, the first network 130 in the networks list 210linked to the country entry 205 is selected. In step 335, it is checkedwhether a network 130 was successfully selected in the network selectionof step 330. If so, then step 340 is entered. A CAMEL-capabilityparameter, representing a level of capability of CAMEL which would givesatisfying CAMEL support to MS 110, is here set to the value of themaximum CAMEL level of capability selected in step 305. Step 345 is thenentered, where capabilities list 215, associated with the network 130selected in step 330, is scanned for a match to the value of theCAMEL-capability parameter. In step 350, it is checked whether a matchwas found. If a match was found, the identity of network 130 selected instep 330 is entered into a preferred networks list in step 355. Step 330is then re-entered, where the next network 130 in network list 210,associated with the country entry 205 selected in step 320, is selected.However, if it is found in step 350 that the network selected in step330 does not support the CAMEL level of capability represented by theCAMEL-capability parameter, then step 360 is entered, where the value ofthe CAMEL-capability parameter is altered in order to represent theCAMEL level of capability next in elaboration to that previouslyrepresented by the CAMEL-capability parameter. In step 365, it ischecked whether the CAMEL level of capability represented by theCAMEL-capability parameter is less elaborated than the minimum CAMELlevel of capability selected in step 305. If so, then step 330 isre-entered where the next network 130 is selected from the network list210 associated with the country entry 205 selected in step 320. If not,then step 345 is re-entered.

[0044] If it is found in step 335 that no network 130 was successfullyselected in step 330, then step 310 is re-entered, where the nextcountry in the international roaming indication is selected. If it isthen found in step 315 that no country was successfully selected in step310, then step 370 is entered. If there are entries in the preferrednetworks list, entered in step 355 described above, then the preferrednetworks list is sent to MS 110 in step 375. The exit-step 380 isentered. If there are no entries in the preferred networks list, thenthe exit-step 380 is entered directly.

[0045] In some cases it might be desirable to allow for theinternational roaming indication to comprise entries representinggeographic areas other than countries, such as e.g. continents orprovinces. The term region will in the following be used to refer to awell defined geographic area, covering either less than an entirecountry, one country, or more than one country. In FIG. 4, a regionarray 400 is shown, the region array 400 shown containing threedifferent region entries 405, each representing a geographic region. Toeach region entry 405 is linked a country list 410, listing thecountries or country included in the region represented by the regionentry 405 to which the country list 410 is linked. When an entry in theinternational roaming indication has been identified as a region, thenthe steps 330 to 365 of FIG. 3 should be run for all entries in thecountries list 410.

[0046] The array presented in FIG. 2 could e.g. be arranged as a CAMELlevel of capabilities array instead of a country array, each entry inthe array representing a CAMEL level of capability and having linkedlists of networks supporting that CAMEL level of capability. Eachnetwork could then have a linked list of identiti(es) of the country (orcountries) in which the network is operated. The flowchart of FIG. 3would then be altered analogously. In another embodiment, all networks130 with which the home network 100 has roaming agreements could bearranged in a network array, each entry in the network arrayrepresenting a network 130 and being linked with information ongeographic coverage as well as CAMEL capabilities of that network 130.The network array could then be scanned for networks 130 having thedesired CAMEL capabilities as well as being operated in the geographicregions indicated in the international roaming indication.

[0047] When the international roaming indication sent to the home mobilenetwork 100 is included in a location update request, the “country”represented by each country entry 205 could advantageously correspond tothe coverage area of a network 130, since the information on geographicareas included in a location update request comprising an identificationof the network 130 with which the MS 110 is presently trying toregister. An example of such a country array 500 is presented in FIG. 5.In the country array 500 of FIG. 5, three different country entries 205are shown. Advantageously, the country array 500 should comprise acountry entry 205 for as many networks 130 in the world, compatible withthe standard of home network 100, as possible, so that when MS 100 istrying to register with any network 130, a country entry 205 will befound corresponding to that network 130.

[0048] To each country entry 205 of FIG. 5 is linked a networks list 210of networks 130 with which the operator of home network 100 has roamingagreements, the networks in the networks list 210 being operated in thesame (or neighbouring) geographic area as the network 130 represented bythe country entry 205. To each country entry 205 is also linked acapabilities list 215, listing the phases, or levels of capabilities, ofa network feature supported by the network 130 associated with thatentry. As an option, a best networks indicator 510 could be linked toeach entry in the networks list 210, the best networks indicator 510indicating whether the network represented by the country entry 205belongs to a group of networks 130 which the operator of home network100 for some reason considers to be favourable over other networks 130.Alternatively, a best networks indicator 510 could be associated witheach country entry 205. Furthermore, a capabilities list 215 could beassociated with each entry in the networks lists 210 instead of witheach country entry 205. If the operator of home network 100 has roamingagreements with the operator of the network 130 represented by thecountry entry 505 to which networks list 210 is linked, this network 130could be included in the networks list 210 (see e.g. network 1 of FIG.5). However, if both the capabilities list 215 and a possible bestnetworks indicator 510 are associated with the country entry 205 ratherthan with the entries in networks list 210, then the country entry 205could be checked directly.

[0049] Each entry in the networks list 210 could be linked to a countryentry 205 representing the network 130 associated with the entry innetworks list 210. When a location update request, comprising a nonpreferred indicator, is received by the home network 100 in which acountry array 500 is stored, the country entry 205 corresponding to thenetwork identity included in the location update request is selected.The networks list 210 linked to country entry 205 is entered, and foreach entry in networks list 210, the country entry 205 linked to thenetworks list entry is checked for network feature capabilities.

[0050] In FIG. 6, a flowchart is shown, describing an exemplaryembodiment of the inventive method in which the international roamingindication is received by the home network 100 via a location updaterequest. The example of FIG. 6 is, for the purpose of illustration only,presented in relation to the network feature known as CAMEL. However,the embodiment of the invention described in FIG. 6 could be used inrelation to any network feature. In step 600, an international roamingindication is received by home network 100 in the form of a locationupdate request sent from a MS 110 to the HLR 125, the location updaterequest comprising a not preferred indicator as well as an identity ofthe network 130 to which the MS 110 is trying to register. This network130 will in the following be referred to as the requesting network. Theinternational roaming indication is then processed by home network 100.In step 605, the CAMEL phases which would be acceptable to thesubscription of services associated with MS 110 is selected. In step610, the country array 500 is scanned, and the country entry 205,corresponding to the identity of the requesting network, is selected (itis here assumed that the requested network is included in the countryarray 500). In step 615, an “update flag”, indicating whether a network130 suitable for communication has been found or not, is set to “false”.Furthermore, a “best networks indication flag”, indicating whether anetwork has been found, suitable for communication and belonging to thegroup of networks that the operator of home network 100 considers to befavourable over other networks, is set to “false”. Step 620 is thenentered, in which the first network 130 in the networks list 210 linkedto the country entry 205, representing the requested network, isselected. This network will in the following be referred to as theexamined network. In step 625, it is checked whether an examined networkwas selected in step 620. If so, step 630 is entered, where thecapabilities list 215, linked to the country entry 205 representing theexamined network, is checked, and the CAMEL phases supported by theexamined network are compared to the CAMEL phases which are acceptableto the MS 110. In step 635, it is then checked whether the CAMEL supportprovided by the examined network is acceptable. If not, step 620 isre-entered, and a new examined network is selected from the networkslist 210 associated with the requesting network. However, if the CAMELsupport provided by the examined network is acceptable, then step 640 isentered, where the examined network is added to a preferred networkslist. Step 645 is then entered, where it is checked whether the updateflag is set to true. If not, then step 650 is entered, where a parameterreferred to as the selected network parameter, representing the network130 selected as the visited network, is set to the identity of theexamined network, and the update flag is set to true. Step 655 is thenentered. If, in step 645, it was found that the update flag was set totrue, step 655 is entered directly. In step 655, it is checked whetherthe best networks flag is true. If not, the best networks indicator 510associated with the examined network is checked in step 660. If the bestnetworks indicator 510 is true, then step 665 is entered, in which theselected network parameter is set to the value of the examined network,and the best networks flag is set to true. If the value of the bestnetworks indicator 510 is false, then step 620 is re-entered and a newexamined network is selected. If, in step 655, it is found that the bestnetworks flag is true, then step 620 is re-entered without entering step660.

[0051] If it is found in step 625 that there are no entries in thenetwork list 210 that have not yet been examined, then step 670 isentered. Here, it is checked whether the update flag is true, i.e.whether any network 130 has been found which would give adequate CAMELsupport to MS 110. If the update flag is false, then a location updateerror message is sent to the MS 110 in step 675, and the procedure isended in step 680. However, if the update flag is true, then step 685 isentered, where the preferred networks list is sent to MS 110. Step 690is then entered, where it is checked whether the selected networkparameter has the value of the identity of the requesting network. Ifso, then a location update confirm message is sent to the MS in step695, confirming to MS 110 that the requesting network is a network 130suitable for communication, and the procedure is ended in step 680. Ifit is found in step 690 that the selected network is not the requestingnetwork then step 697 is entered, in which a message is sent to the MS110 informing the MS 110 of that the requesting network is not suitablefor communication, and providing the MS 110 of the identity of theselected network, with which MS 10 should try to register. This messagecould e.g. be a location update error message including information onthe identity of the selected network. The procedure is then terminatedin step 680.

[0052]FIG. 7 shows an exemplary sequence diagram describing thesignalling between the MS 110, the HLR 125 and an application server 700when the international roaming indication is included in a locationupdate request sent from a MS 110 towards the core network. Theapplication server 700 could be co-located with the HLR 125, orimplemented elsewhere. A location update request, including a nonpreferred indicator, is sent from MS 110 to HLR 125, see message 7 a.The reception of the location update request at the HLR 125 thentriggers the sending of an international roaming request, see message 7b, comprising the identity of the MS 110 and the identity of the network130 to which the MS 110 is trying to register. The international roamingrequest is then processed at the application server 700. The identity ofthe selected network is then returned to the HLR 125 in an internationalroaming result message, see message 7 c, and included in a locationupdate result message, see message 7 d, sent to the MS 110. Theapplication server 700 also sends a preferred networks list to the MS110, see message 7 e. The preferred networks list could e.g. be sent tothe MS 110 by using the SMS (Short Message Service) protocol.

[0053] Instead of sending the preferred networks list to the MS 110 in aseparate message, as is done in the embodiments described by FIG. 3, 6and 7, the preferred networks list could be included in the locationupdate result message. Step 375 of FIG. 3, step 685 of FIG. 6, as wellas message 7 e of FIG. 7, would then be superfluous. Alternatively, onecould choose not to send any preferred networks list at all, but onlyinclude the identity of the selected network in a location update resultmessage.

[0054] In an embodiment where a parameter in the location update requestis used as the international roaming indication, a mechanism could beintroduced which informs the HLR 125 when the network featurecapabilities of the visited network are altered. The HLR 125 could thensend an instruction to the application server 700 to check whether thesupport for the network feature offered by the visited network is stillacceptable. If not, the HLR 125 could decide to cancel the registrationof MS 110 in the visited network. This would cause the MS 110 to try toregister with the networks included in the preferred networks liststored in the MS 110. If the MS 110 is not successful in registeringwith any of those networks, MS 110 would search for other networks and,if a network is found, send a location update request including a notpreferred indicator towards the HLR 125. In this way, it is ensured thata MS 110 is always registered with a network 130 which gives adequatesupport for a certain network feature, if present.

[0055] Further alterations to the procedures described by FIGS. 3 and 6could also be made without departing from the spirit of the invention.One could e.g. introduce a step in FIGS. 3 and 6 where the size of thepreferred networks list to be sent from the home network 100 to the MS110 is checked, in order to avoid sending a preferred networks listwhich is too large to be stored in its entirety in the MS 110.Furthermore, one could introduce a procedure which estimates the numberof countries contained in the international roaming indication, and thenmakes a decision on how many networks 130 operated in each country canbe entered in the preferred networks list. In the procedure described inFIG. 3, a counter could be introduced that counts the number of networks130 from each network list 210 that has been entered in the preferrednetworks list. Alternatively, instead of entering step 330 of FIG. 3when step 355 has been executed for the first time, step 310 could beentered, so that only one network 130 per country entry 205 is enteredinto the preferred networks list. Furthermore, one could introduce linksto each country entry 205 of the country array 200, the linksrepresenting neighbouring countries, and then perform the steps 330 to365 for those neighbouring countries, in order to add networks 130operated in the neighbouring countries to the preferred networks list.Similarly, links to country entries 205 representing adjacent networks130 could be introduced to each country entry 205 in country array 500.

[0056] When compiling a preferred networks list, the networks 130entered into the list could be placed in order of preference accordingto a predefined criterion or criteria. This could be especiallyinteresting of no criterion is used when entering the networks 130 intothe networks lists 205 of country array 200 or 500. An arranging stepcould then e.g. be entered between the steps 370 and 375 of FIG. 3(steps 670 and 685 in FIG. 6), where the networks added to the preferrednetworks list in step 355 (step 640) could be placed in order ,accordingto the predefined criteria. Examples of criteria to be considered couldbe the level of radio coverage of the networks 130 or the ownership ofthe network 130. Some of the networks 130 could possibly have the sameowner as home network 100, and others may be owned by operators withwhich home network 100 has favourable agreements.

[0057] Step 305 of FIG. 3, in which the maximum (most elaborated) andminimum (least elaborated) CAMEL level of capability that would satisfythe needs of MS 110 is selected, does not have to be performed each timean international roaming indication is received by the home network 100.The selection of maximum and minimum CAMEL level of capabilities coulde.g. instead be performed upon changes to the CAMEL capabilities of homenetwork 100, or upon changes to the subscription of services of MS 110.The results could then be stored in the home network 100 and retrievedupon the reception of an international roaming indication.

[0058] The steps 305, 340, 345, 350, 360 and 365, in which the CAMELneeds of MS 110 is compared to the CAMEL support provided by networks130, could possibly be performed in a different way. E.g., in step 305,all the CAMEL level of capabilities which are acceptable to 110 could bestated and explicitly compared to the CAMEL level of capability providedby the networks 130.

[0059] The inventive method and apparatus described above could be usedselecting a visited network with regard to more than one networkfeature. Each entry in the network list 210 associated with a countryentry 205 in the country arrays 200 and 500, could then have one link toa capabilities list 215 for each network feature. The checks made insteps 330 to 365 of FIG. 3, and step 635 to 640 of FIG. 6, would thenhave to be adjusted analogously.

[0060] Furthermore, the inventive method and apparatus could be used forcompiling a preferred networks list for a subscription to serviceswithout prior reception of an international roaming indicationassociated with the subscription. The operator of home network 100 coulde.g. send preferred networks lists to its subscribers, the networks 130included in the preferred networks lists selected on the basis of inwhich geographic areas subscribers to services in home network 100 mostoften perform international roaming as well as on the basis of theindividual network feature needs of each subscription.

[0061] One skilled in the art will appreciate that the present inventionis not limited to the embodiments disclosed in the accompanying drawingsand the foregoing detailed description, which are presented for purposesof illustration only, but it can be implemented in a number of differentways, and it is defined by the following claims.

1. A method for selecting a visited mobile radio network for a mobilestation performing international roaming, the mobile station beingassociated with a subscription to services in a home mobile radionetwork, in which method the need of a network feature of thesubscription is considered in selecting the visited mobile radionetwork, said method being characterised by the following steps of:receiving, in the home mobile radio network, an international roamingindication associated with said subscription, the international roamingindication comprising information on geographical region(s); and saidinformation on geographical region(s) being considered, together withthe network feature need of the mobile station, in selecting the visitedmobile radio network.
 2. The method according to claim 1, furthercomprising the following steps: compiling a list of preferred mobileradio networks, comprising the identity of at least one mobile radionetwork, the at least one mobile radio network supporting said need of anetwork feature of the subscription; sending said list of preferredmobile radio networks to the mobile station; and storing said list ofpreferred mobile radio networks at the mobile station.
 3. The methodaccording to claim 2, wherein the identities of mobile radio networks inthe list of preferred mobile radio networks are placed in order ofpreference according to a predefined criteria.
 4. The method accordingto claim 2, wherein the mobile station, upon failure to register withthe home mobile radio network, selects a mobile radio network from saidlist of preferred mobile radio networks as the visited mobile radionetwork with which the mobile station should try to register.
 5. Themethod according to claim 1, wherein the international roamingindication is a location update request comprising an identity of themobile station, the identity of the mobile radio network to which themobile station is trying to register and a not preferred indicator; andthe information on geographic region(s) consists of the identity of themobile radio network to which the mobile station is trying to register.6. The method according to claim 5, wherein the identity of a selectedvisited mobile radio network is included in a location update resultmessage sent to the mobile station in response to receiving saidlocation update request.
 7. The method according to claim 1, wherein: aset of mobile radio networks, out of which the visited mobile radionetwork can be selected, is arranged in an array, each array entryrepresenting a geographic area and each mobile network in the set beingassociated with at least one array entry representing a geographic areain which the mobile radio network is operated, each mobile radio networkin the set being further associated with information on the networkfeature support provided by said mobile radio network.
 8. The methodaccording to claim 7, wherein the geographic area represented by anarray entry corresponds to the coverage area of a mobile radio network,the mobile radio network not necessarily being included in the set ofmobile radio networks; and the coverage area of each of the mobile radionetworks in the set is represented by an entry in the array.
 9. Themethod according to claim 7, wherein to each mobile radio network in theset is associated an indicator indicating whether the mobile radionetwork is a favourable mobile radio network; and the value of theindicator is taken into account in selecting a visited mobile radionetwork.
 10. The method according to claim 7, wherein the mobile radionetworks in the array are placed in order of preference according to apredefined criteria.
 11. The method according to claim 1, wherein saidnetwork feature is the Customized Application for Mobile networkEnhanced Logic (CAMEL).
 12. The method according to claim 1, whereinsaid network feature is the General Packet Radio Service (GPRS).
 13. Asystem for mobile radio communication comprising mobile radio networks,each mobile radio network enabling mobile radio communication for mobilestations registered with the mobile radio network, said systemcomprising means for taking into account the needs of a network featureof a mobile station when selecting a visited mobile radio network forsaid mobile station, said system being characterised by said means fortaking into account comprises receiving means for receiving aninternational roaming indication associated with said mobile station,said international roaming indication comprising information ongeographical region(s).
 14. The system of claim 13, wherein said meansfor taking into account further comprises a first storage for storinginformation on which (if any) level(s) of capability of said networkfeature that each of the mobile radio networks in a set of mobile radionetworks supports; and a second storage for storing information onlevel-of-capability needs of a subscription, associated with said mobilestation, with regard to said network feature.
 15. The system of claim13, wherein the receiving means comprises means for receiving a locationupdate request comprising a not preferred indicator.
 16. The system ofclaim 15, said system further comprising sending means for sending alocation update result message to the mobile station, said locationupdate result message comprising information on a visited mobile radionetwork with which said mobile station should try to register.
 17. Thesystem of claim 13, wherein said means for taking into account furthercomprises means for compiling a list of preferred mobile radio networks,containing identities of mobile radio networks which gives support forthe network feature needs of said mobile station; and sending means forsending the list of preferred mobile radio networks to the mobilestation.
 18. The system of claim 17, wherein the sending means furthercomprises means for sending a location update result message comprisingsaid list of preferred mobile radio networks.
 19. The system of claim13, further characterised in that said network feature is the CustomizedApplication for Mobile network Enhanced Logic (CAMEL).
 20. A mobilestation for communicating in a mobile radio system, the mobile stationbeing associated with a subscription to services in a home mobile radionetwork and comprising a storage for storing a list of preferred mobileradio networks, said mobile station being characterised by thecapability of sending a location update request comprising a notpreferred indicator to said home mobile radio network when trying toregister with a mobile radio network other than the home mobile radionetwork or the mobile radio networks listed in the list of preferredmobile radio networks.